Technical Abstract:
The intensive hands-on activities of greenhouse tomato propagation and production favor the spread of mechanically transmitted pathogens, particularly Clavibacter michiganensis subsp. michiganensis (Cmm), viruses, viroids, and Botrytis cinerea. These pathogens can spread during crop handling, grafting and de-leafing via pruning knives, shears, other tools, machinery, equipment, and workers’ hands and clothing. Most tomatoes grown in greenhouse production systems are grafted, and the process is also becoming popular in cucurbits to manage soilborne diseases. However, the grafting process is a particularly high-risk activity for transmission of these pathogens. Some common disinfectants used in crop production facilities include alcohols, halogens, peroxides, quaternary ammonium, sodium hypochlorite, and botanicals. Their efficacy against the full range of tomato pathogens found in these systems has not been determined. There are a number of factors to consider when selecting a disinfectant, including effectiveness against target diseases, corrosiveness, residual activities, and worker and environmental safety. This research aims to identify disinfectants that: (1) require very short contact time; (2) are broadly effective against viruses, viroids, bacteria, and fungi; (3) are not dangerous to workers; 4) are not corrosive to infrastructure or phytotoxic to plants; and (5) are economical. Commercial disinfectants were examined for efficacy in eliminating Cmm, viruses, viroids and B. cinerea. Replicated in vitro experiments were conducted using pure cultures of Cmm and B. cinerea, and in vivo experiments were conducted on tomato plants using Pepino mosaic virus (PepMV) and zucchini plants using Squash mosaic virus (SqMV) at 0 sec (immediately after treatment), 30 sec and 1 min exposure times of different disinfectants. KleenGrow, Green-Shield, BioSide, Des-O-Germ, Menno Florades, Menno-Terforte and Clorox killed Cmm and Botrytis cinerea cultures at all exposure times. Octave, Trisodium Phosphate, StorOx, Menno-Terforte, Menno Florades, Non-Fat dry milk, and Virkon S reduced the infection of PepMV on inoculated tomato plants and Virkon S, SaniDate, Green-Shield, Vortexx, Octave, BioSide, Lysol, Des-O-Germ, and Menno-Terforte reduced SqMV infection at all exposure times. Additional trials are underway to determine effectiveness of those disinfectants in preventing Cmm, viruses, viroids, and B. cinerea plant-to-plant spread by cutting tools.